An algal-bacterial symbiotic system of carbon fixation using formate as
a carbon source
Abstract
Algae are an attractive option for CO2 sequestration due to their
natural ability to simultaneously fix CO2 and accumulate algal biomass
for value-added products. However, the commercial implementation of such
technology for efficient capture of CO2 from fossil-derived flue gases
is not a reality yet due to several major challenges, such as low
gas-liquid mass transport efficiency and relatively high light
irradiance demand of algal growth. This study explored an
algal-bacterial symbiotic system to utilize formate, a potential
intermediate liquid compound of CO2, as carbon source to support
microbial growth. The algal-bacterial assemblage, after an adaptive
evolution using the formate medium, demonstrated a new route to
assimilate CO2 without using high pH cultivations and promote biomass
production under low light irradiance condition. The formate based
culture system not only resolves CO2 mass transfer limitation, but also
expels algae grazers in non-sterilized cultivation conditions.
Continuous cultivation of the assemblage on formate led to a carbon
capture efficiency of 90% with biomass concentration of 0.92 g/L and
biomass productivity of 0.31 g/L/day, which is significantly better than
the control cultivation on saturated CO2. In addition, isotope tracing
and microbial community analysis offer new insights into formate
metabolism and algal-bacterial symbiosis under light and carbon
conditions. This study demonstrates a promising route of using
electrochemical-derived formate to support algal biorefining.